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(Circulation. 1995;92:113-121.)
© 1995 American Heart Association, Inc.

Articles

Surgical Management of Aortic Dissection During a 30-Year Period

James I. Fann, MD; Julian A. Smith, MS; D. Craig Miller, MD; R. Scott Mitchell, MD; Kathleen A. Moore, BS; Gary Grunkemeier, PhD; Edward B. Stinson, MD; Philip E. Oyer, MD; Bruce A. Reitz, MD; Norman E. Shumway, MD

From the Department of Cardiovascular and Thoracic Surgery, Stanford University School of Medicine, Stanford, Calif.

Correspondence to D. Craig Miller, MD, Department of Cardiothoracic Surgery, Cardiovascular Research Center, Stanford University Medical Center, Stanford, CA 94305-5247.

	Abstract

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Background Certain recent studies have demonstrated improved surgical outcome in patients with aortic dissection. We analyzed the surgical survival rates of patients with acute aortic dissections and the late prognosis of those with aortic dissection during a 30-year period.

Methods and Results Between 1963 and 1992, 360 patients (256 men and 104 women; mean±1 SD age, 57±14 years) underwent surgery for aortic dissection: 174 patients had an acute type A (AcA), 46 an acute type B (AcB), 106 a chronic type A (ChA), and 34 a chronic type B (ChB) aortic dissection. The overall operative mortality rate was 24±8% (26±3% for AcA, 39±8% for AcB, 17±4% for ChA, and 15±6% for ChB, [±70% confidence limit]). The operative mortality rates for patients with acute aortic dissection (AcA or AcB) were assessed for five time "windows": 1963 to 1972 (42±8%), 1973 to 1977 (37±8%), 1978 to 1982 (15±6%), 1983 to 1987 (27±6%), and 1988 to 1992 (26±6%). Logistic regression analysis suggested that the low operative mortality rate during the 1978-to-1982 interval occurred by chance. Multivariate analysis showed earlier operative year, hypertension, cardiac tamponade, renal dysfunction, and older age were independent determinants of operative death. Actuarial survival rates (including early deaths) after 5, 10, and 15 years for AcA patients were 55%, 37%, and 24%; for AcB, 48%, 29%, and 11%; for ChA, 65%, 45%, and 27%; and for ChB, 59%, 45%, and 27%. Multivariate analysis revealed that older age and previous operation were significant predictors for late death. Freedom from reoperation for all patients was 84%, 67%, and 57% at 5, 10, and 15 years, respectively.

Conclusions Although the operative mortality rate decreased over time for patients with aortic dissection, the risk for those with acute aortic dissection during the last 10 years (1983 to 1992) is probably more realistic than that observed in the preceding 5-year interval (1978 to 1982). The operative mortality rates for patients with chronic aortic dissection have remained relatively static. Earlier diagnosis of acute aortic dissection before development of cardiac tamponade and renal impairment is critical to improve the operative salvage rate. Long-term outcome still is not optimal, which emphasizes the need for better serial postoperative aortic imaging surveillance and medical follow-up and blood pressure control.

Key Words: aorta • surgery • aneurysm • arteries • cardiovascular diseases

	Introduction

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Certain reports have demonstrated substantially improved surgical outcome in patients with aortic dissection over time.^{1 2 3 4 5 6} The surgical mortality rates in the "current era" have been estimated to be in the range of 3% to 7% for patients with acute type A dissections and 6% to 13% for those with acute type B dissections.^{1 2 3 6 7} These lower mortality rates were attributed to advances in diagnosis, improved surgical techniques and perioperative management, and increased surgical experience.^{1 2 3 5 6 8} Early detection and intervention before the development of catastrophic complications have been emphasized, but it is not clear whether this has contributed to better outcome. After the initial repair, the biological nature of aortic dissection mandates continued long-term medical surveillance; repeat "downstream" surgical intervention before aortic rupture or extension or development of ischemic complications is paramount. Analyses of surgical survivors have shown a late survival rate of approximately 80% at 5 years and 65% at 10 years.^{3 6 9} The question remains whether the long-term outcome for these patients has improved over the years given the enhanced medical awareness, closer postoperative surveillance of the aorta, and changing guidelines for surgical intervention. The previous Stanford experience demonstrated better early surgical results, particularly in the acute dissection subgroups and especially during the 1977-to-1982 time period.¹ Our series has been expanded to encompass a 30-year time span.

	Methods

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Three hundred sixty patients (256 men and 104 women) underwent surgery for spontaneous aortic dissection at Stanford University Medical Center between 1963 and 1992. The diagnosis of dissection was confirmed with aortography, computed tomography, magnetic resonance imaging, transesophageal echocardiography, surgical findings, or autopsy reports. The acuity and type of aortic dissection were classified according to previously published criteria: dissections involving the ascending aorta were considered to be type A, and those without ascending aortic involvement were considered to be type B.¹⁰ The dissection was acute if symptoms occurred within 14 days and chronic if longer than 14 days. All clinical data were obtained by retrospective review of hospital records, and postoperative follow-up was obtained by written and/or telephone communication. Follow-up was complete in 98% of patients and extended to a maximum of 30 years (mean±SD, 5.1±5.5 years; total, 1840 patient-years).

One hundred seventy-four patients (48%) had an acute type A aortic dissection (AcA), 46 (13%) an acute type B (AcB), 106 (30%) a chronic type A (ChA), and 34 (9%) a chronic type B (ChB). The mean age of all patients was 57±14 years (±1 SD; range, 15 to 86 years). The age distribution of patients is shown in Fig 1. For the 40 patients with the Marfan syndrome, the average age was 35±9 years (range, 15 to 54 years).

View larger version (53K): [in this window] [in a new window]   Figure 1. Bar graph of age distribution of patients with aortic dissection.

Selected preoperative clinical patient characteristics and complications based on acuity and type of aortic dissection are listed in Table 1. Hypertension was the most common predisposing medical disorder, occurring in more than 50% of the patients. Aortic rupture occurred in one third of patients with AcA dissections, and one half of these patients developed cardiac tamponade. Aortic valvular insufficiency was common in patients with type A dissections, occurring in approximately 40% of cases. The location of the primary intimal tear was in the ascending aorta in 246 patients (68%), the arch in 28 (8%), the descending thoracic aorta in 71 (20%), the abdominal aorta in 2 (1%), and not specifically determined in 13 (3%).

View this table: [in this window] [in a new window]   Table 1. Selected Preoperative Clinical Characteristics and Complications According to Acuity and Type of Aortic Dissection

Surgical outcome was measured in terms of operative mortality, late survival, and rate of late reoperation. To compare our more recent surgical results with those in our early experience, trends in operative mortality rates for the acute subgroups (AcA or AcB) were examined during five arbitrary time "windows": 1963 to 1972, 1973 to 1977, 1978 to 1982, 1983 to 1987, and 1988 to 1992. For each time interval, an expected risk of operative death was calculated and compared with the observed mortality rate. In addition, the operative mortality rate of patients who sustained clinically important preoperative complications of the aortic dissection (including aortic rupture, cardiac tamponade, compromise of visceral perfusion, renal dysfunction, congestive heart failure, and shock)^{1 11} was compared with that of patients without such complications within each time window.

Patient Management and Type of Operation
Although there was substantial variability in the surgical techniques that have evolved over these 30 years, the following reflects our general approach. The ascending aorta in patients with type A dissections or the proximal descending aorta in those with type B dissections (and the intimal tear, if identified) were resected, and a tubular Dacron interposition graft was placed.^{12 13} For patients with type B dissections, a left posterolateral thoracotomy and partial cardiopulmonary bypass (femoral-femoral, pulmonary artery-femoral, left atrial [LA]-femoral, or LA-distal aortic graft) was used, if feasible. Attempts were made to repair and resuspend the native aortic valve, whenever possible, except in cases of the Marfan syndrome, severe annuloaortic ectasia, or intrinsic underlying aortic valve disease.¹⁴ Nevertheless, a number of patients required aortic valve replacement (AVR): 36 patients (21%) with AcA dissections underwent aortic valve resuspension, 35 patients (20%) with AcA required AVR (separate AVR or composite valve graft), 5 patients (5%) with ChA dissections underwent resuspension, and 48 (45%) of those with ChA underwent AVR. Composite valve graft replacement with reimplantation of the coronary arteries was performed in 5 patients (3%) with AcA and 11 patients (10%) with ChA dissections but never included the "graft inclusion" or wrapping "Bentall" technique.^{15 16 17} Concomitant replacement of the aortic arch was performed in 8 patients with AcA, 4 with AcB, 10 with ChA, and 1 with a ChB dissection. In patients with acute dissection, it was often possible to reconstruct the dissected coronary ostia; however, coronary artery bypass graft surgery was necessary in 21 patients. The aortic cross-clamp times, cardiopulmonary bypass times, and whether the intimal tear was able to be resected in each subgroup are given in Table 2.

View this table: [in this window] [in a new window]   Table 2. Selected Surgical Characteristics According to Acuity of Dissection and Type of Aortic Dissection

Statistical Analysis
Continuous data are expressed as mean±1 SD. Operative mortality was defined as death occurring in the hospital or within 30 days of the operation. Relevant mortality rates are presented with ±70% CL (confidence limits). Statistical comparisons between categorical parameters were performed using ² contingency analysis. Differences in the operative mortality rates for the five time windows were analyzed by comparing the expected risk of early death with the actual mortality using Pearson's ² analysis. To further examine the variability in the operative mortality rates over time, a stepwise logistic regression analysis was performed for all patients as well as for those with acute aortic dissection based on the multivariate predictors of operative death (vide infra). The logistic regression equation provides an expected probability of operative death for each patient based on his or her particular set of risk factors during one time window, as incorporated by this statistical model. For a given subset of patients (eg, those in a particular time frame), the average of these probabilities gives the expected mortality for the group. To determine whether a particular group fared better or worse than expected (by the model), the average of the probabilities is compared with the observed mortality for that group (number of operative deaths divided by the number of patients). Twenty-eight preoperative factors were analyzed by univariate analysis followed by a Cox model multivariate analysis with respect to operative mortality, late mortality, and risk of reoperation; these factors included site of tear, type A or B, acute or chronic, sex, emergency operation, year of operation, hypertension, angina, acute myocardial infarction, congestive heart failure, pulmonary disease, diabetes, cigarette smoking, the Marfan syndrome, New York Heart Association functional class, acute aortic insufficiency, cardiac tamponade, loss of peripheral pulse(s), renal dysfunction, stroke, shock, compromise of visceral perfusion (by angiogram), compromise of peripheral perfusion (by angiogram), rupture, age, chronic aortic insufficiency, previous cardiac or thoracic aortic operation, and type and acuity of dissection (AcA versus AcB versus ChA versus ChB). Survival and event-free survival probability estimates were determined by life-table analysis; variability of these estimates was expressed as ±1 SEM. The actuarial curves were compared with the use of a Gehan test. P.05 was considered to be statistically significant after correction for multiple comparisons.

	Results

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Early Results
Operative Mortality and Morbidity
The overall hospital mortality rate for all of the surgical patients during this 30-year period was 24±8%: 26±3% for those with AcA dissections, 39±8% for AcB, 17±4% for ChA, and 15±6% for ChB. The operative mortality rate for the subgroup of patients with the Marfan syndrome was 10±5% (4 of 40): 19±10% (3 of 16) for AcA, 0% (0 of 2) for AcB, 6±6% (1 of 18) for ChA, and 0% (0 of 4) for ChB. The operative mortality rates for patients with acute aortic dissections according to age are illustrated in Fig 2, and the causes of hospital death are listed in Table 3. Myocardial failure (including low cardiac output) was the most common cause of early mortality. Postoperative complications included 44 cases of reexploration for hemorrhage, 13 patients with postoperative myocardial infarctions, 12 patients with strokes, and 42 patients who required tracheostomy for prolonged ventilatory support (Table 4).

View larger version (40K): [in this window] [in a new window]   Figure 2. Bar graph of surgical mortality rates (±70% CL) of patients with acute aortic dissection according to age.

View this table: [in this window] [in a new window]   Table 3. Causes of Hospital and Late Death

View this table: [in this window] [in a new window]   Table 4. Early Postoperative Complications by Acuity and Type of Dissection

The operative mortality rate for patients with acute aortic dissections (type A or B) was assessed during the five time windows (Fig 3): it decreased to a nadir (15±6%) in the 1978-to-1982 interval, but subsequently stabilized at 26±6% in the most recent time intervals. The operative mortality rates for each individual subgroup during these five time intervals are summarized in Table 5. Although the operative mortality rates during the 30-year period have fluctuated (with an overall decrease) in the acute dissection groups, the operative mortality risk of those with chronic dissections has remained relatively lower and unchanged throughout the years (15±4% during the last 15 years). The incidence of selected preoperative complications in patients with acute aortic dissections (ie, aortic rupture, cardiac tamponade, compromised visceral or renal perfusion, congestive heart failure, and shock) during each time window is given in Table 6. The operative mortality rates for patients with and without these complications (in the acute dissection groups) in each time window are shown graphically in Fig 4. For each interval, the patients with complications fared worse than did those without complications, as intuition would dictate (however, in 1973 to 1977, this difference did not achieve statistical significance). In fact, the relatively low mortality risk for patients without complications remained comparatively stable throughout the entire 30-year period, whereas the mortality rates of those patients with complications fluctuated substantially; interestingly, this risk increased during the last 10 years compared with the earlier 1978-to-1982 interval.

View larger version (34K): [in this window] [in a new window]   Figure 3. Bar graph of surgical mortality rates (±70% CL) of patients with acute aortic dissection at each of the five time windows.

View this table: [in this window] [in a new window]   Table 5. Surgical Mortality for the Five Time Windows

View this table: [in this window] [in a new window]   Table 6. Incidence of Pertinent Complications Over the Five Time Windows for Patients With Acute Aortic Dissection

View larger version (39K): [in this window] [in a new window]   Figure 4. Bar graph of surgical mortality rates (±70% CL) of acute aortic dissection patients with and without preoperative complications, including aortic rupture, cardiac tamponade, compromise of visceral perfusion, renal dysfunction, congestive heart failure, and shock.

For patients with acute aortic dissections (AcA or AcB), Pearson's ² analysis was used to compare the expected risk of operative death with the actual outcome at each time interval. For all time intervals, the observed operative mortality rates were not significantly different than the expected risk (P=.10). Furthermore, a logistic regression analysis incorporating the five predictors of operative mortality (earlier operative year, hypertension, cardiac tamponade, renal dysfunction, and older age) did not reveal significant differences between the expected and observed operative mortality rates over time. The actual operative mortality rates for all patients and for the acute subgroups in the 1978-to-1982 interval were not significantly different than the predicted rates (P=.12 and P=.08, respectively) (Fig 5). It thus is likely that the apparently lower operative mortality observed during the 1978-to-1982 time window occurred due to chance or perhaps due to some other imponderable factor.

View larger version (33K): [in this window] [in a new window]   Figure 5. Bar graph of stepwise logistic regression analysis to achieve an expected (or predicted) estimate of the surgical mortality and the observed (or actual) mortality of patients with acute aortic dissection for each time window.

Multivariate Analysis
For all patients, the Cox model multivariate analysis showed that earlier operative year, hypertension, cardiac tamponade, renal dysfunction, and older age significantly increased the likelihood of operative death. The only potentially modifiable factors were cardiac tamponade and renal dysfunction, which theoretically might be reduced with earlier diagnosis and intervention. Site of tear and pulmonary disease, which were significant in our previous analyses,¹ did not emerge as risk factors for early death in this expanded series.

Late Results
Overall Survival
Actuarial survival rates (including hospital deaths) for all patients at 1, 5, 10, and 15 years were 69%, 57%, 39%, and 23%, respectively (Fig 6). For AcA patients, these respective rates were 67%, 55%, 37%, and 24%; for AcB, 56%, 48%, 29%, and 11%; for ChA, 76%, 65%, 45%, and 27%; and for ChB, 78%, 59%, 45%, and 27%. The late survival rates for all discharged patients at 1, 5, 10, and 15 years were 92%, 76%, 52%, and 30%, respectively (Fig 7). For AcA patients, these respective rates were 91%, 75%, 51%, and 32%; for AcB, 93%, 80%, 48%, and 18%; for ChA, 93%, 79%, 54%, and 33%; and for ChB, 93%, 70%, 54%, and 32%. There was no statistically significant difference, interestingly, in the long-term survival rates among the four subgroups (for discharged patients, P=NS). The causes of late death are listed in Table 3; approximately one third of deaths were cardiac related, and at least 15% of deaths were due to complications or extension of the aortic dissection (including sudden, unexplained deaths). Unrelated deaths, which accounted for 32% of the deaths in patients with type A and 38% of those with type B dissections, were due to trauma, malignancy, or other chronic systemic illnesses.

View larger version (15K): [in this window] [in a new window]   Figure 6. Plot of actuarial late survival estimates for all patients with aortic dissection (±1 SEM).

View larger version (15K): [in this window] [in a new window]   Figure 7. Plot of actuarial late survival estimates for all discharged patients with aortic dissection (±1 SEM).

Multivariate Analysis
For all patients, the multivariate analysis showed that older age and previous operation were significant risk factors for late death. Long-term actuarial survival curves with and without previous operation are shown in Fig 8; the small difference in these survival estimates is noteworthy. Interestingly, stroke, chronic renal dysfunction, remote myocardial infarction, and earlier operative date, which were independent predictors of late death in our 1985 analysis,⁹ did not emerge as risk factors in this larger series.

View larger version (22K): [in this window] [in a new window]   Figure 8. Plot of actuarial late survival estimates (±1 SEM) for discharged patients with (PREV SURG) versus without (NO PREV SURG) previous cardiac or thoracic surgery.

Late Reoperation
Sixty-two patients (30 patients with initial AcA repair, 6 patients with AcB repair, 17 patients with ChA repair, and 9 patients with ChB repair) required a total of 75 late reoperations related to aortic valve disease or persistent and/or recurrent aortic dissection or thoracic or abdominal aortic problems. Nine patients had multiple reoperative procedures. The overall reoperative mortality rate for these 62 patients was 35±6%. Freedom from late reoperation for all patients was 95%, 84%, 67%, and 57% at 1, 5, 10, and 15 years, respectively (Fig 9). For patients initially operated on for AcA dissections, these respective rates were 94%, 83%, 65%, and 65%; for those with AcB dissections, 92%, 83%, 76%, and 76%; for ChA, 96%, 88%, 65%, and 52%; and for ChB, 100%, 83%, 71%, and 27%. The multivariate analysis revealed that younger age was the only significant risk factor indicating a higher likelihood of reoperation over time. Site of intimal tear (arch), which was a significant variable in our previous analysis,⁹ was not an independent risk factor for reoperation in the present study.

View larger version (16K): [in this window] [in a new window]   Figure 9. Plot of actuarial estimates of freedom from reoperation (±1 SEM) for all patients with aortic dissection.

	Discussion

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Various surgical groups have reported improved survival of patients undergoing operation for aortic dissection in more recent years.^{1 2 3 4 5 6 7} At Stanford between 1963 and 1976, the operative mortality rates were 38% for patients with AcA dissection and 50% for those with an AcB dissection; these rates decreased to 7±5% and 13±12%, respectively, for the period between 1977 and 1982.¹ Similarly, Crawford and colleagues^{2 3} reported operative mortality rates of 33% for patients with AcA dissection and 45% for AcB before 1986, compared with less than 5% and 6%, respectively, for selected patients undergoing surgical intervention after 1986. For their chronic dissection subgroups, the operative mortality rates also decreased from 12% to 17% before 1986 to 4% to 8% in the latter time period.² These impressive operative results were attributed to increased surgical experience and advances in diagnosis, surgical techniques, myocardial protection, and perioperative management.^{1 2 5 6 7}

Based on our recent experience, the trend toward higher operative survival rates previously observed¹ was not sustained. Multivariate analysis demonstrated that our contemporary operative results are significantly better compared with earlier years, but the reported lower mortality rates in the 1977-to-1982 time period¹ have not been improved on subsequently. It is important to note, however, that although lower, our operative mortality rates during the 1978-to-1982 time interval were also not significantly different from the expected values (as predicted by the logistic regression analysis). It is thus likely that the lower operative mortality rates during that particular interval might have occurred due to chance or lower overall patient risk. Nevertheless, the fluctuations in the operative mortality rates are of interest. Over time, the incidence of germane preoperative complications did not demonstrably increase or decrease; on the other hand, the number of patients referred from outlying hospitals has increased. The higher operative mortality rates for patients with acute aortic dissections during these recent time windows coincided with the trend in the mortality rates of patients who had suffered more major preoperative complications. Not surprisingly, patients with acute dissection who did not sustain a serious complication fared comparatively well during the entire 30-year time span. In contrast, the complicated cases have been associated with a significantly higher operative mortality risk, a finding that has been consistent throughout the years. Therefore, to effect a significant increase in overall patient salvage rate, it is necessary either to improve the surgical outcome of those patients with preoperative complications or to convert these patients into the "uncomplicated" category, which can be accomplished only by intervention before dissection-related complications develop.

Changing patient substrate may provide another explanation for the fluctuations observed in the operative survival rates. Abrupt alterations in referral patterns occurred just after the nadir in our operative mortality risk (1977-to-1982 time period). Starting in 1982, a large northern California health maintenance organization assumed surgical treatment of most patients with cardiovascular surgical problems at a centralized location, including uncomplicated patients (relatively lower-risk patients) with aortic dissection, whereas the high-risk patients were still referred to our institution. At the same time, a helicopter-based air ambulance transport program was established that permitted more rapid transport of critically ill patients from hospitals within a 400-km radius who otherwise might not have survived ground transport. It is thus plausible that our patient population became a higher-risk cohort, but we could not discern this change in objective terms. Other, as yet unidentified and possibly imponderable, patient referral factors could also have played a role in these changing trends.

Our previous analysis indicated that renal dysfunction, renal or visceral ischemia, site of intimal tear (arch descending >ascending), cardiac tamponade, earlier operative date, and pulmonary disease significantly increased the probability of operative mortality.¹ The analyses of Crawford and colleagues^{2 3} demonstrated that surgery before 1987, severe symptoms, coronary artery disease, diabetes mellitus, reoperation for bleeding, cardiac complications, and stroke were independent risk factors for early mortality.² In our current 30-year series, earlier operative date, hypertension, cardiac tamponade, renal dysfunction, and older age were also determinants of early death. Combining our observations with those of Crawford and colleagues, potentially modifiable preoperative variables include only cardiac tamponade, renal dysfunction, visceral ischemia, cardiac complications, stroke, and advanced aneurysm symptoms, the incidence of which theoretically can be minimized by earlier diagnosis and surgical intervention.^{1 2 8}

Concerning the optimal management of patients with AcB aortic dissection, identification of high-risk patients has been difficult, and debate continues as to whether surgical or medical treatment is the most prudent approach.^{11 18 19 20 21 22 23} A retrospective cooperative study from Stanford and Duke Universities demonstrated that the medical and surgical approaches had equivalent early results in the low-risk (uncomplicated) subgroup in terms of 30-day hospital mortality rate (9% for the surgical cohort versus 16% for those treated medically) and long-term survival.¹¹ We concluded that initial medical management might be preferable in this patient population from the standpoint of morbidity and medical economics.¹¹ Similarly, Crawford and colleagues suggested that uncomplicated patients with AcB aortic dissection undergo initial medical therapy, reserving surgical intervention for those who fail medical management, develop complications or aneurysmal enlargement, or have the Marfan syndrome.² Conversely, early operation may be more appropriate in younger, healthier patients with AcB aortic dissection, in whom the long-term survival advantage could be expected to be the greatest.^{21 23} If surgery is reserved solely for patients with major dissection complications, the overall emergency salvage rate cannot be expected to exceed 20% to 25%.^{1 21 22 24} This finding was also evident in the present study in that patients who presented with complications before operative intervention did substantially worse than did those without complications. Based on the Stanford-Duke findings,¹¹ however, the mortality associated with an early aggressive surgical approach in low-risk patients is no higher than that associated with medical therapy. Thus, early surgical replacement of the proximal descending aorta theoretically may confer some long-term protection by reducing the incidence of aneurysmal dilatation of other aortic segments, extension of dissection, or late ischemic complications.^{21 23} Furthermore, compliance with medical therapy cannot be ensured indefinitely; unfortunately, deaths occur frequently due to late aortic rupture and renal failure, and subsequent operation may be necessary for aneurysmal aortic dilatation (which may possibly confer a higher surgical mortality risk than that associated with operation in the acute stage).

In patients with chronic aortic dissection, surgery may be indicated earlier in younger asymptomatic, low-risk patients with substantial aneurysmal dilatation of dissected aortic segments, particularly in those with the Marfan syndrome.^{2 21 25} The overall operative mortality rate in this group of patients has remained relatively low, especially during the last 15 years in our experience (eg, 15±4%). The Stanford criteria for surgical intervention include all symptomatic patients and those asymptomatic patients with ascending or descending false aneurysmal dilatation more than twice the diameter of the contiguous "normal" aorta. On the other hand, high-risk surgical candidates are followed for the development of symptoms or complications and are treated expectantly; Crawford and colleagues have similarly suggested that older, fit patients with dissection undergo surgery when they have smaller aortic diameters than previously recommended.²

In the present study, the late survival rates of discharged patients were 76%, 52%, and 30% at 5, 10, and 15 years, respectively. There were no significant differences in late survival rate based on dissection acuity and type. Among all patients with aortic dissection, previous cardiac operation and older age were predictors of late mortality. Stroke, chronic renal dysfunction, remote myocardial infarction, and earlier surgical date, which were risk factors for late death in our 1985 analysis,⁹ were not significant determinants. The relatively low long-term survival rates, however, remain sobering, particularly in the AcB subgroup. Improved survival rates could potentially pivot on closer aortic imaging surveillance and earlier reintervention before the development of complications, such as aortic rupture, which affected a substantial minority of patients (±15% of late deaths).

Estimates of freedom from late reoperation for all patients were 84%, 67%, and 57% at 5, 10, and 15 years, respectively, with no significant differences among patients in the various subgroups. The only risk factor in this analysis that portended a high risk of reoperation was younger age. Previous studies suggested a correlation between the presence of the Marfan syndrome and reoperation; this finding is probably the result of the younger age of these patients.^{2 9} Recently, Crawford and colleagues suggested that a more extensive aortic replacement, resecting all dilated segments of the dissected aorta at the initial operation, may be associated with a lower probability of reoperation.^{2 3} If there is enlargement or impending rupture of the aortic arch, the operation must include arch replacement using profound hypothermic circulatory arrest. In cases where the aortic dissection involves the arch or if the tear is in the arch, we along with others have advocated arch resection in selected, younger patients.^{3 5 25 26} Also, we agree with the aggressive posture of Crawford and colleagues regarding earlier reoperation, in view of the fact that 88% of ruptured dissecting thoracic aneurysms occurred in those less than 10 cm in size and 23% occurred in those less than 6 cm in their series.²

Serial and indefinite computed tomography or magnetic resonance imaging of the aorta are mandatory in the long-term follow-up of patients with either medically or surgically treated aortic dissection.^{13 19 20 23 27 28} Because most patients have persistence of the intimal flap and false lumen flow postoperatively after surgery in the distal aorta, information over time regarding changes in aortic size are of particular importance regardless of whether the patient is symptomatic. The decision for repeat surgical intervention, however, has to be individualized. In an otherwise healthy patient with minimal comorbidity, an aggressive surgical approach is appropriate to decrease subsequent risk of rupture or late ischemic complications; on the other hand, in elderly patients with modest and stable aneurysmal dilatation of the aortic false lumen, it is probably more prudent to monitor the patient closely and intervene once symptoms develop.

In summary, despite the fluctuations in the surgical mortality rates over time, particularly for patients in the acute aortic dissection subgroups, there has been an improvement in surgical results during this 30-year period, whereas the surgical mortality risk for patients with chronic aortic dissections has remained comparatively low. Although the multivariate analysis confirmed a decreasing surgical mortality rate over time for patients with aortic dissections, the risk for those with acute aortic dissections during the last 10 years (1983 to 1992) has plateaued and may be more realistic than that we reported earlier (1978 to 1982). Earlier diagnosis of acute aortic dissection before the development of cardiac tamponade and renal or visceral flow impairment remains essential if we are to improve these surgical survival rates. The relatively low long-term late survival rates are disappointing and may be enhanced in the future by closer surveillance of the aorta and earlier reintervention before the development of dissection-related complications. The reoperation rate may be reduced in the future if concomitant arch involvement is addressed at the initial operation.

	References

Top Abstract Introduction Methods Results Discussion References

 

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